Images are used to communicate information and ideas. Images, including print pictures, film negatives, documents and the like, are often digitized to produce a digital image that can then be instantly communicated, viewed, enhanced, modified, printed or stored. The flexibility of digital images, as well as the ability to instantly communicate digital images, has led to a rising demand for improved systems and methods for film processing and the digitization of film based images into digital images. Film based images are traditionally digitized by electronically scanning a film negative or film positive that has been conventionally developed using a wet chemical developing process, as generally described below.
Undeveloped film generally includes a clear base and one or more emulsion layers containing a dye coupler and a photosensitive material, such as silver halide, that is sensitive to electromagnetic radiation, i.e., light. In color films, independent emulsion layers are sensitized to different bands, or colors, of light. In general, one or more emulsion layers are sensitized to light associated with the colors of red, green and blue. When a picture is taken, the photosensitive material is exposed to light from a scene and undergoes a chemical change. The greater the intensity of light interacting with the photosensitive material, the greater the chemical change in the photosensitive material. The photographic film can then be chemically processed to produce a fixed image of the scene based on this chemical change.
In a traditional wet chemical developing process, the film is immersed and agitated in a series of tanks containing different processing solutions. The first tank typically contains a developing solution. The developing solution chemically reacts with the exposed silver halide to produce elemental metallic silver grains in each emulsion layer of the film. The metallic silver grains form a silver image within each emulsion layer of the film. The by-product of the chemical reaction combines with a dye coupler in each emulsion layer to create a dye cloud. The color of the dye cloud is complementary to the band of light the emulsion layer has been sensitized to. For example, the red sensitized layer typically produces a cyan dye image, the green sensitized layer a magenta dye image, and the blue sensitized layer a yellow dye image. The density of the silver image and the corresponding dye image in each emulsion layer are directly proportional to the intensity of light the film was exposed to. The developing process is generally stopped by removing the film from the developer tank and rinsing the developing solution from the film with water or an acidic solution.
Conventional wet chemical developing processes then removes both the silver image and the undeveloped silver halide grains from the film to produce a film negative having only a dye image within the film negative. To remove the silver image and undeveloped silver halide, the developed film is immersed and agitated in a tank of bleaching solution. The bleaching solution chemically oxidizes the metallic silver grains forming the silver image and converts the metallic silver grains into silver halide. The bleached film is then immersed and agitated in a tank of fixer solution. The fixer solution removes the silver halide from the film by dissolving the silver halide crystals. The fixer solution is thereby contaminated with dissolved silver compounds and becomes a hazardous waste byproduct of the wet chemical developing process. The film is then washed, stabilized and dried to produce a conventional film negative. The film negative can then be used to produce a corresponding image on photographic paper by methods known to those skilled in the art.
Conventional film digitization processes scan the film negative using a conventional electronic scanner to produce a digital image that electronically represents the photographic image. Conventional electronic film scanners generally operate by directing white light through the film negative. The light interacts with the dye image and the intensity of light transmitted through the film is recorded by a sensor that produces individual red, green and blue color data. The sensor color data is used to produce the digital image.
A relatively new process under development is digital film processing (DFP). DFP systems scan the film using light during the development process. DFP systems apply a thin coat of one or more film processing solutions to the film and then scan the film. Neither the processing solutions nor the silver compounds are substantially removed from the film before or after scanning the film. DFP systems may be designed in a number of configurations depending upon the method of film processing and the method of scanning the film. For example, the film may be processed by applying a developer solution, a developer solution and fixer solution, a developer solution, fixer solution, and
The DFP scanning process is generally accomplished by measuring infrared light reflected from the developed silver image in the front and back emulsion layers, and measuring the infrared light transmitted through the film. The reflected and transmitted light measurements of the film provide data on the blue, red, and green sensitized emulsion layers, respectively. The measured reflected and transmitted light data is processed to produce the digital image.